Question: How do clouds stay in the sky?

Freya Addison answered on 18 Nov 2019:

This is a really interesting question. A cloud isn’t the same as a pond in the sky. It is formed of lots of very tiny water droplets with gaps between them. Water is evaporated into the atmosphere, it is taken up on convection currents (hot air rises, cold air sinks). But as a gas, they don’t want to be near each other, so they rise and they spread out, so the average temperature goes down. When the temperature is cool enough, the water cools down to become a liquid, but because it was excitable it is no longer with many other water droplets, so it is very tiny. These tiny droplets will fall because of gravity but they don’t fall very fast. If they get caught in another current of air they will just flow along with it. Eventually what happens, due to flows and condensation, the water droplets will eventually gather together to form clouds, but they are still very small droplets, with warmer air in-between providing lift. Eventually, as a cloud gathers more and more droplets, it gets heavier, there are more collisions, and you get bigger droplets, which fall faster and need bigger lifts, so these form the rain clouds.
I recommend this article, with the video clip of how to weigh a cloud as demonstrated by my colleague Dr Jim McQuaid.
https://theconversation.com/curious-kids-how-do-the-clouds-stay-up-in-the-sky-99964